Means for protecting operators&#39; ringing leads from short circuits.



W. DEA

GUITS.

ING OPERATORS RINGING LEADS FROM SHORT CIR MEAN S FOR PROTECT 93%,Qfii3u APPLICATION FILED AUG. 9, 1905. v

Patented Aug. 24, 1909.

@FFEIQE.

Specification of Letters Patent.

Patented eug. 2e, NW9.

' Applicationfiled Auguste, Seria1'.flo.273,55.

To all whom it may concern: i

Be it lrnownthat 1, WILLIAM N. DEAN, a citizen of the United States, residing at l llyria, in the'county of Lorain and State of Ohio, have invented certain new and useful Improvements in Means for Protecting Operators Ringing Leads from Short Circuits of which the following is a specification, reference being had therein to the accompanying drawing. I

My invention relates to telephone exchange systems, and particularly to the signaling apparatus and circuits employed. therein.

It has for its object the provision of means for the protection of operators ringing leads from short circuit.

Heretoforc it has been customary to connect ordinary incandescent lamps in the ringing leads or branches from the powerboard to the operators keys. Some pro- 'vision of this kind is necessary, for the reason that the resistance of lines varies widely, and if an operator should ring out over a line which was short-circuited or grounded, the lead would obviously also become shortcircuitcd, but. by including a sullicient resistance in the path of the ringingcurrent any injurious rise thereof due to a shor circuit would be prevented.

The objections to the use of incandescent lamps in the manner statedare as follows: l irstfthe voltage and etl'cctivc outputof the generators must be made Very much higher than they would otherwise have to be. in order to ovcrcoinc the resistance of the lamps when ringing; second. a lamp resistance acts in aiuanner directly the reverse of what is most desired, because its resistance falls when hot. Thus. when ringing over a long line, of high resistance the lamp resistance will be at its maximum, thereby cutting down the eilcctive voltage thrown on the line; and when ringing over a short line, of low resistance, the lamp heats up and lowers its resistance. thereby raising the etlcctive voltage on the line, and still further increasing the current.

My invention obviates the disadvantages of the lamp resistances, providing :lior a normal low rcsistancc, rising to a maximum when the line resistance is liclow a definite l prcdcteri'nincd quiintity.

' Briefly stated, it comprises a low resistance relay with a back contact armature. connected in series in the ringing branch or lead. The relay is so adjusted that it will not pull up under normal ringing condltlons, but when the operator rings on a short-circuited line the consequent large flow of current .eli'ect-ively energizes the relay, which pulls up its armature, thus breaking its own circuitto release the armature, and so on after the manner of a buzzer. The continued, vibration or" the armature introduces a very higl'i resistance at-Tthe contacts, which to prevent burning I preferably make of carbon.

As a supplemental feature of the protective scheme, I provide means for indicating a short-circuit to the operator so that it can be immediately reported to the wire chief.

' My invention is illustrated in the accon panying drawing, wherein the figure is 'a diagram showing :1 subscribers line and substation appantus. with a central otiice connective circuit and ringing key.

In the drawing, A indicates the subscribers station. provided with the usual transmitter, T, receiver. R, switchhook, H, and ringer, Q. The line wires 1 and 2 terminate at the central oiiice at t-he springs j and 7" of the line jack J, which may also have a test thimblc 7' Vi' heu in a condition of disuse, the jack springs are closed upon the contact anrils forming terminals of the circuit.- of the line annunriator. L. For simplicity of illustration 1 have shown an annunciator of the HHUJDGIO drop shutter type, but it is to be understood that my invention applicable to any type oi. system. and that its essential features are unchanged in any case, Whether the switchboard be a transfer or a multiple board. and its circuits supplied with current. ii-(an a central otiice battery for all purposes or from local batteries and magneto generators for talking and signaling respectively.

For intcrcoimeeting the lines at the central oiiicc cord circuits are provided, ea h with terminal plugs l and P. ha vine; istip and sleeve contacts councctcd together respcw lively by the comluctors l and l-6. For a magneto S 'l0i1l such as the diagram indicate a i'lWH'lllQj-(Hll annunciator is bridged mlt the cord at ll. A suitable listening hey connected in cach cord, but this is omitted item the illustration.

The opcratofs ringing hey is shown at K. This has the usual or any desired form oi lu lion or lcvcr manipulated by tho operator to move the contact springs in and 7a, which normally rest on contact points forming the terminals of the cord conductors 5 and 6 whereby the tips 39 and p and the sleeves 79 and p are joined. When the springs 70 and k are separated they leave the normal .or

cord terminals and make contact with the terminals of the generator circuit or ringing lead 7+8, thus connecting the generator G through conductors 3 and at to the plug P and so to the line 1-42, assuming the plug to have been inserted in the jack J.

The system thus far described is old and well known, and as l have stated may be varied in many Ways without affecting the essential features of my invention. According to present p actice, an incandescent lamp would be interposed in the path 7 between the generator bus 14 and the key K. I have discarded the lamp, however, .and in its Y place I introduce the relay M, Whose Windstand sparking without injury.

1' spring m ings are connected on one side to the wire '7 and on the other through-Wire 9 with its own armature m, or a contact moved thereby. The armature normally rests against a back contact m and the actual contact :t'aces. or points I makerather heavy and of carbon, to enable them to pass a heavy current and From the contact at the Wire 14 passes to the generator G, this and the Wire 12 in the drawing indicating the buses. The wire 12' has the ground tap l0.

For the "mrpose of indicating a short-circuited or groimdcd line when ringing, I connect a high resistance relay N around the contacts m its circuit being from wire 14 through wire .3 and by wire 11 to the armature m. The armature n of this relay controls the continuity oi a local circuitl516, containing a signal lamp 0 and a suitable source of current, and is normally retracted by the spring 91/.

The relay M is so designed that a large current is required to operate it, this being accomplished in a manner well known to all engineers, by suitably arranging its magnetic circuit and adjusting the retractile Upon a. predetermined rise in current, however, it will operate by vibrat ing its armature as a buzzer, opening and closing the contacts at m with great rapidity. Such rapid opening and closing introduces a very highresistance at the cohtacts, which. may beregulated by adjusting the amplitude and rate of the vibrations. 3y suitably proportioning the turns of wire in the winding, the mass and relative effects of theparts of the magnetic circuit, and the strength of the spring myli may produce a resistance inversely proportional to the current or to, that of the line over which the current passes, the lines hein g thus ballasted during ringing. .t will be observed that the operation of this regulating relay M in a shunt in-any convenient part of the switchboard may be designated as the ringing lamp, and remain unobserved except in cascsoi line'trouble, when it will light up, and the operator being thereby notified may report the same. The rise of current in the line thus strengthens the flux in the relay M, which by vibrating the armature m raises the resistance in the shunt around relay N, causing arise in current therein which eventually overcomes the spring a and lights the ringing lamp 0. The-operation is symmetrical and properly directed to produce symmetrical ringing eli'ects. I believe that I am the first to succeed in at taining this desirable object, and I shall accordingly claim the same broadly.

I do not desire to limit myself to the use of the indicating relay or signal with the regulating relay or resistance, as the latter may obviously be employed alone with advantage.

Many variations may be made in rangement and manner of use of the invention, and all such are contemplated by me.

lt will be observed'in the beginning of.

this specification that I have referred to the inclusion of lamp resistancesm operators ringing leads. I have also pointed out the objections to this arrangement, one of which is that the lampresistance varies inversely as the current. The distinctive feature of my present invention is that it covers a compensating resistance, the lamps heretofore employed being merely limiting resistances, with their only variation in a reverse direction to that which would tend to compensate for variation in the line resistance.-

I shall employ the Word compensating hereafter in my claims, in order to mark this distinctive feature oi. ditlerence. I may here define the term compensating resistance as one which varies inversely as that with which it is to be used, seas to partially or wholly equalize the total resistance in the ringing circuit for lines of dlflerent lengths.

Having described my invention, What I claim, and desire to secure by Letters Patent of the United States, 1s:

1. In a telephone system, a hue circuit, a source of current supply therefore a CUT1U- lion 't'rom such source to the hue a compenthe 11-- nection from such source to the line, a compensating resistance=interposed in such connection, and electromagnetic means in such the line increases.

connection for increasing such resistance as the current delivered from such 3] In a telephone exchange system, a pluralit'y of line circuits, and. central office connectlve circuits for inter-connecting the lines, a source of calling current at the central office, means to connect the same with a connective circuit, and a magnetically controlled variable resistance in said connection, together with an indicating device adapted to indicate the condition of the resistance device.

4. In a telephone system, a line circuit, a

source'of ringing current, a switch for con-- necting said source to the line, and a relay having its circuit completed and its operation continuously controlled through a back con tact of its own armature, interposed in the circuit between the source and the switch.

5. In a tele hone system, an operators connective corc circuit, comprising connecting cords with terminal plugs, a ringing key connected to the same, and connections from said ringing key to a suitable source of ringing current; together with a buzzer connected in the lead between the source and the ringing key.

6. As a means for protecting telephone operators ringing leads, a variable resistance device connected therein and comprising a buzzer relay having carbon contacts.

4. As a means for protecting telephone operators ringing leads, a variable resistance device connected therein and comprising a buzzer relay having carbon contacts in series with the winding of its magnet.

8. in a telephone exchange system, an operators cord circuit and ringing key, and mnnections therefrom to a ringing generator, a buzzer relay connected between the generator and the ringing key to serve as a variable resistance, and an indicating device controlled by said relay.

source to 9. In a telephone exchange system, an operators cord circuit and ringing key, and

connections therefrom to a ringing genen' ator, a buzzer relay connected between the generator and the rin ing key to serve as a variable resistance, a an indicating device connected so as to be actuated when the buzzer relay operates.

10. In a telephone exchange system, an operators cord circuit and ringing key, and

connections therefrom to a ringang generator, a buzzer relay connected between the generator and the ringing key'to serve as a variableresistance, and an indicating device connected in a shunt around the contacts of the buzzer.

11. In a telephone exchange system, an operators cord circuit and ringing key, a generator of ringing current, suitable connections from said source to said ringing key, and a buzzer relay included in said connections, the windings of said relay being of relatively low. resistance.

12. In a telephone system, a connective circuit and a ringing key or switch therefor, a ringing generator and connections therefrom to the switch, a variable resistance normally at a minimum value included in said connections, and an indicating device in a shunt around said resistance.

13. In a telephone system, a connective circuit and a ringing key or switch there for. a ringing. generator and connections therefrom to the switch, a variable resistance normally at a minimum value included in said connections, and an indicating device of relatively high resistance in a shunt around said variable resistance device.

14. In a telephone system, a ringing key or switch, a ringing generator, and ringing leads extending from said generator to said switch, a low-wound buzzer relay with carbon contacts connected in one of said ringing leads. a relatively high-wound magnet connected around the contacts of said buzzer relay. and asignal controlled by said highwound magnet.

In testimony whereof I aiiix my signature in presence of two witnesses.

WILLIAM IV. DEAN.

\Vitnesses:

A. D. T. LIBBY, Gno. A. Soovinnn. 

